Method for quantifying LBP in body fluids

ABSTRACT

The present invention provides a method for quantifying the presence of extracellular LBP in body fluids including blood in a subject comprising conducting an LBP immunoassay on plasma obtained from said subject.

[0001] This application is a continuation-in-part of U.S. Ser. No. 08/377,391 filed Jan. 24, 1995, which is in turn a continuation-in-part of U.S. patent application Ser. No. 08/186,811 filed Jan. 24, 1994, all of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to methods for determination of the presence of Lipopolysaccharide binding protein (LBP) in body fluid samples including blood samples.

[0003] Lipopolysaccharide (LPS) is a common component of the outer membrane of Gram-negative bacteria and is responsible for many of the pathologic effects associated with gram-negative bacterial infection and endotoxemia. Because of the association between bacterial infection and sepsis, attempts have been made to correlate serum/plasma levels of endotoxin with disease. Typically, endotoxin levels have been measured using the Limulus amebocyte lysate (LAL) assay, in which endotoxin initiates a coagulation cascade that can be measured physically, turbidimetrically, or spectropliotometrically, Despite these attempts, however, no reliable correlations between endotoxin levels and sepsis severity or outcome have been identified. This is most likely due to the fact that (i) endotoxin levels in septic patients are very low (>10 pg/L), several serum proteins interfere with the proteolytic LAL cascade, (iii) endotoxin, once in contact with blood, can be “detoxified” by interaction with a variety of blood components, including high-density lipoprotein (HDL) and low-density lipoprotein (LDL) and (iv) endotoxin from different gram-negative organisms varies in its ability to trigger the LAL cascade. Thus, the absolute levels of endotoxin in a patient sample may not correspond to the actual concentrations of bioactive endotoxin present in vivo.

[0004] Two related proteins have been identified in humans and other animals that bind LPS with high affinity. These two proteins, Lipopolysaccharide binding protein (LBP), and bactericidal/permeability increasing protein (BPI) have roughly the same molecular weight and share 45% amino acid homology, yet exhibit distinct physiological differences. LBP is a 60 kD glycoprotein synthesized in the liver, while BPI is found in the azurophilic granules of neutrophils. LBP is found in the serum of normal humans at levels of 5-10 μg/mL but can reach levels of 50-100 μg/mL in septic patients. Schumann et al., Science, 249:1429 (1990) disclose the amino acid sequences and encoding cDNA of both human and rabbit LBP. Like BPI, LBP has a binding site for lipid A and binds to the LPS from rough (R-) and smooth (S-) form bacteria. Unlike BPI, LBP does not possess significant bactericidal activity. BPI has been observed to neutralize and inhibit the production of TNF resulting from interaction of LBP with LPS and CD14 on monocytes and macrophages. Marra et al., J. Immunol. 148: 532 (1992), Weiss et al., J. Clin. Invest. 90: 1122 (1992). In contrast, LBP is observed to enhance LPS-induced TNF production. Wright et al., Science, 249:1131 (1990). Thus, in contrast to BPI, LBP has been recognized as an immunostimulatory molecule. See, e.g., Seilhamer, PCT International Application WO 93/06228 which discloses a variant form of LBP which it terms LBP-β. Also of interest to the present invention are Ulevitch, PCT International Application WO 91/01639 which discloses, among other things, anti-LBP antibodies as an anti-sepsis therapeutic agent and U.S. Pat. No. 5,245,013 which relates to LBP and discloses antibodies which immunoreact with a polypeptide having homology to LBP.

[0005] LBP has been characterized in the art as an “acute phase protein”, that is one of many plasma proteins (such as C-reactive protein, fibrinogen and serum amyloid A) that increase in concentration in response to infectious and non-infectious tissue destructive processes. As such, it would be anticipated that LBP levels would be elevated in samples from patients suffering from a number of autoimmune diseases such as rheumatoid arthritis and lupus erythematosus.

[0006] Of interest to the present invention are disclosures related to the assaying of BPI activity in subjects. von der Mohien et al., Abstract, 13th International Symposium on Intensive Care and Emergency Medicine, Brussels (March 1993) discloses the results of assays for serum levels of BPI in patients with gram-negative sepsis and healthy subjects. The abstract disclosed that no BPI was detectable under the conditions of the assay in the serum of healthy subjects while circulating BPI was detected in all septic patients. Also of interest is the disclosure of co-owned and copending U.S. patent application Ser. No. 08/175,276 filed Dec. 29, 1993 which is a continuation-in-part of application 08/125,677 filed Sep. 22, 1993 the disclosures of which are hereby incorporated by reference. Those patent applications disclose that levels of BPI in blood plasma samples correlate with the presence or absence of sepsis while levels of BPI in blood serum samples do not. The patent applications teach that levels of BPI present in serum are not representative of endogenous extracellular levels of BPI in circulating blood while levels of BPI in plasma are.

[0007] Also of interest to the present invention are the disclosures of Leturcq et al., Keystone Tahoe Endotoxin Conference, Mar., 1-7, 1992 (Abstract) in which the generation of monoclonal antibodies to human LBP is reported. Also reported is the screening of normal human serum samples for the presence of LBP. LBP levels for normal serum samples were reported to range from 1 μg/mL to 24 μg/mL with an average of 7 μg/mL. Further of interest is the disclosure of Richard Ulevitch at the American Society for Microbiology General Meeting in Atlanta, Ga. May 16-21 (1993) at which data was presented on LBP and soluble CD14 levels in the serum of septic and healthy individuals The average soluble CD14 and LBP concentrations in the serum of healthy adults were 1 μg/mL and 7 μg/mL respectively. The average soluble CD14 and LBP concentrations in the serum of septic patients were reported to be 2 μg/mL and 55 μg/mL respectively.

[0008] Geller et al., Arch. Surg., 128: 22-28 (1993) disclose experiments in which the induction of LBP mRNA was studied in three models known to induce acute phase responses: (1) LPS injection; (2) Corynebactelium parvum injection; and (3) turpentine injection. The publication reports that LEP mRNA is induced during hepatic inflammation and suggest that LBP is an acute-phase protein important in regulating the in vito response to endotoxin.

[0009] Gallay et al., Infect. Immun. 61:378-383 (1993) disclose that an acute phase response in mice injected with silver nitrate induced LBP synthesis, and that LBP levels increase approximately 10-fold over normal levels after an acute-phase response.

[0010] There exists a desire in the art for methods for determining the exposure of subjects to endotoxin and for distinguishing the effects of exposure to endotoxin from other acute phase physiologic responses. Also desired are methods for diagnosing the presence or severity of gram-negative sepsis in a subject and for predicting the prognosis of a subject suffering from sepsis.

SUMMARY OF THE INVENTION

[0011] The present invention provides methods for specifically determining exposure of a subject to endotoxin by assaying for LBP. The invention further provides methods for screening for exposure to gram-negative bacterial endotoxin in an acute phase response in humans by assaying for LBP. Specifically, the method comprises the steps of determining the concentration of LBP in a sample of body fluid from the subject and correlating the concentration of LBP with a standard indicative of the exposure to endotoxin. Such standards can include a subjective standard for a given subject determined by LBP levels of that subject in a pretreatment state such as prior to undergoing surgery. Exposure to endotoxin as a consequence of such surgery can be determined by comparing post-surgical LBP levels with the standard established prior to surgery for that subject. Where access to a pretreatment standard level of LBP is not available for a given individual, objective standards based upon population or subpopulation averages may be applied for comparison. One such standard can be a concentration greater than approximately 15 μg/mL in human plasma or serum, as determined herein for LBP values in subjects suffering from numerous disease states. Subjects exhibiting LBP levels above that standard could presumptively be diagnosed as suffering from exposure to endotoxin while those having levels below that standard would not be. It is clear that alternative standards could be established depending upon the desired sensitivity and selectivity of an assay method and upon the subpopulation in which a given subject falls. For example, standards might be established at different levels for different ages, genders, ethnicities and underlying health conditions of various subpopulations. Moreover, it should be understood that standard levels will differ according to the identity of the particular body fluid which is assayed.

[0012] The invention further provides methods for diagnosing the presence or severity of sepsis in a subject comprising the steps of determining the concentration of LBP in a sample of body fluid from the subject and correlating the concentration of LBP with a standard indicative of the presence or severity of sepsis. The invention further provides methods for predicting the prognosis of a subject suffering from sepsis comprising the steps of determining the concentration of LBP in a sample of body fluid from the subject and correlating the concentration of LBP with a standard indicative of the prognosis of a subject suffering from sepsis.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 depicts the dose-response curves for rLBP, rLBP₂₅, rBPI and rBPI₂₃ in LBP sandwich assays;

[0014]FIG. 2 depicts LBP levels (mean ± standard error) in the plasma of healthy human subjects and human subjects suffering from various disease states;

[0015]FIG. 3 depicts LBP levels (mean ± standard error) in healthy subjects treated with LPS;

[0016]FIG. 4 depicts comparative survival in suspected gram-negative sepsis patients classified as having either high or low levels of plasma LBP; and

[0017]FIGS. 5a-5 c depict LBP, C-reactive protein (CRP) and fibrinogen levels (mean ± standard error) in healthy, rheumatoid arthritic and septic subjects.

DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention relates to methods for quantifying the presence of LBP in body fluids including blood. While the assay can be used to determine the presence and quantity of LBP which has been administered therapeutically, it is particularly useful for quantifying the presence of endogenous LBP in circulating blood as an indication of exposure of a subject to endotoxin. Moreover, quantifying the presence of LBP is contemplated to be useful in diagnostic and prognostic methods for evaluating gram- negative sepsis patients.

[0019] The present invention provides a sandwich ELISA assay for human LBP which exhibits high assay sensitivity, high specificity, and excellent reproducibility. As used herein “LBP” quantitated according to assay methods includes native LBP, recombinant LBP, LBP fragments and analogs as well as other LBP proteins and protein products.

[0020] The amino acid and nucleotide sequence of recombinant LBP are set out in co-owned and copending U.S. patent application Ser. No. 08/029,510 filed Jun. 17, 1993 as shown in SEQ ID NOS: 1 and 2 herein. A recombinant LBP amino-terminal fragment is characterized by the amino acid sequence of the first 197 amino acids of the amino-terminus of LBP as set out in SEQ ID NOS: 3 and 4 the production of which is described in co-owned and copending U.S. patent application Ser. No. 08/079,510 filed Jun. 12, 1993 the disclosure of which is incorporated herein. Such LBP protein products may be readily quantified using assays including immunological assays and bioassays in the subnanogram per mL range. Immunological assays capable of quantifying LBP are preferably carried out by enzyme linked immunosorbant (ELISA) sandwich assays but competitive assays and immunological assays utilizing other labelling formats may also be used. Preferred assays of the invention utilize anti-LBP antibodies, including monoclonal antibodies and affinity-purified rabbit polyclonal antibodies. Rabbit polyclonal anti-LBP antibodies may be prepared according to conventional methods using LBP as an immunogen. Non-immunological methods may also be used to assay for LBP. As one example, Ulevitch et al., U.S. Pat. No. 5,245,013 disclose assay methods comprising binding of LBP to LPS and separating the complex by a centrifugation density gradient method. As another example, Geller et al., Arch. Surg. 128: 22-28 (1993) disclose LBP bioactivity assays in which IL-6 and TNF upregulation are measured.

[0021] Body fluids which can be assayed for the presence of LBP include whole blood with blood serum and blood plasma being preferred. Because LBP is a serum protein it is contemplated that it could be excreted and that analysis of LBP levels in urine may provide diagnostic and prognostic utility. The LBP immunoassays of the invention may also be used to determine the concentration of LBP in other body fluids including, but not limited to lung lavages, vitreous fluid, crevicular fluid, cerebrospinal fluid, saliva, sputum, ascites, amniotic fluid and synovial fluid.

[0022] Because LBP has been characterized as an “acute phase protein” it would be expected that LBP levels would be elevated in subjects suffering from autoimmune diseases. As one aspect of the present invention it has been found that LBP levels are not substantially elevated over normal in subjects with malignancies, immune diseases or syndromes, viral conditions and other conditions, such as, specifically, acute lymphoblastic leukemia (ALL), acute graft versus host disease (aGvHD), chronic lymphocytic leukemia (CLL), cutaneous T-cell lymphoma (CTCL), type 1 diabetes, aplastic anemia (AA), Crohn's Disease, psoriasis, rheumatoid arthritis (RA), sclerodermna, systemic lupus erythematosus (SLE), pregnancy and acquired immune deficiency syndrome (AIDS). In these patients with a condition not associated with endotoxin and thus not associated with elevated LBP levels, exposure to endotoxin is expected to produce a rise in LBP levels over the normal baseline LBP values for that condition. Thus, an elevation in LBP levels for these and other patient populations, like healthy subjects (i.e., subjects with no evidence of disease), is expected to be diagnostic of an exposure to endotoxin.

[0023] The invention thus contemplates use of the LBP assay for distinguishing conditions associated with endotoxin from conditions (either acute phase or non-acute phase) not associated with endotoxin. The invention also contemplates the detection of exposure to endotoxin in healthy subjects or in patients with a condition not associated with endotoxin. The invention further contemplates multiple determinations of LBP levels of a subject over time, either to monitor for potential development of a condition associated with endotoxin or to monitor a subject for the severity or prognosis of a condition associated with endotoxin.

[0024] Certain subjects tentatively identified as suffering from gram-negative sepsis but ultimately identified as suffering from gram-positive sepsis also had elevated LBP levels. It is noted that translocation of bacteria and/or endotoxin from the gut into the bloodstream can occur in any infection. Thus, infections due to gram-positive bacteria or fungi may also lead to the presence of endotoxin or gram-negative bacteria in the blood and, therefore elevated levels of LBP.

[0025] The present invention is based in part upon the observation that serum and plasma levels of LBP directly correlate with a subject's exposure to biologically active LPS. Moreover, LBP levels appear to correlate with survival in suspected gram-negative sepsis patients. For example, subjects with levels of circulating LBP below 27.3 μg/mL (the median value for 58 subjects suffering from gram-negative sepsis) tended to have a greater 14 day survival than did those subjects with levels of LBP above that median. Further, for example, when a plasma LBP threshold level was set at 46 μg/mL, those subjects having a pretreatment LBP plasma level less than 46 μg/mL had a significantly greater survival rate (p=0.004) over a 27 day period than did those subjects having a pretreatment plasma LBP level greater than 46 μg/mL.

[0026] It is further contemplated by the invention that elevated levels of LBP may result from exposure to larger amounts of endotoxin, and may therefore be diagnostic of greater infection and/or endotoxemia severity. Elevated levels of LBP may also be used to indicate the suitability of using antibiotics directed against gram-negative bacteria or other therapeutic agents targeted directly to endotoxin such as BPI or anti-endotoxin antibodies including the monoclonal antibody E5.

[0027] Other aspects and advantages of the present invention will be understood upon consideration of the following illustrative examples. Example 1 relates to the preparation of affinity purified rabbit anti-BPI antibodies; Example 2 relates to the biotin labeling of such antibodies; and Example 3 relates to EUSA procedures utilizing such antibodies. Example 4 relates to the comparative immunoreactivity of rLBP, rLBP₂₅, rBPI AND rBPI₂₃. Example 5 relates to the measurement of rLBP spiked into pooled human plasma; and Example 6 relates to the comparison of LBP levels in human plasma and serum. Example 7 relates to the clinical correlations of endogenous LBP immunoreactivity with sepsis and other disease states in human plasma; and Example 8 relates to the effect of LPS administration on endogenous LBP levels in healthy subjects. Example 9 relates to clinical correlations between plasma LBP levels and survival in suspected gram-negative sepsis patients; and Example 10 relates to clinical correlations of acute phase proteins in healthy rheumatoid arthritic and septic patients.

EXAMPLE 1 Preparation of Affinity Purified Rabbit Anti-rLBP Antibody

[0028] According to this example affinity purified rabbit anti-rLBP antibody was prepared. Specifically, rLBP (20 mg) produced according to co-owned and copending U.S. patent application Ser. No. 08/079,510 filed Jun. 17, 1993, the disclosure of which is hereby incorporated by reference was coupled to 10 mL of cyanogen bromide-activated Sepharose 4B (Sigma Chemical Co., St Louis, Mo.) in 0.2 M bicarbonate, pH 8.6, containing 0.5 NaCl. Approximately 94% of the rLBP was coupled to the resin. Pooled antisera (125 mL) from two rabbits, immunized initially with rLBP₂₅ produced according to the methods of U.S. patent application Ser. No. 08/079,510 filed Jun. 17, 1993 and thereafter with rLBP, were diluted with an equal volume of phosphate buffered saline, pH 7.2 (PBS). A portion (50 mL) of the diluted antisera was passed through the 10 mL rLBP-Sepharose column; the column was then washed with PBS and bound antibodies were eluted with 0.1 M glycine, pH 2.5. Collected fractions were immediately neutralized with 1 M phosphate buffer, pH 8.0. Peak fractions were identified by measuring absorbance at 280 nm according to the method of Harlow et al., Antibodies: A Laboratory Manual, Cold Springs Harbor Laboratory Press, New York, p. 312 (1988). After several sequential column cycles, the affinity purified rabbit anti-LBP antibody was dialyzed against PBS-azide pH 7.2.

EXAMPLE 2 Preparation of Biotin Labeled Rabbit Anti-rLBP Antibody

[0029] this example twenty milligrams of affinity purified rabbit anti-rLBP antibody produced according to the method of Example 1 was incubated with 2 mg of biotinamidocaproate N-hydroxysuccinimide ester (Sigma Chemical Co., St. Louis, Mo.) in 11 mL of 0.1 M sodium bicarbonate pH 8.3 for two hours at room temperature. Unconjugated biotin was removed and the alkaline buffer exchanged by fractionating the reaction mixture on a PD-10 column (Pharmacia Biotech Inc., Piscataway, N.J.) equilibrated with PBS containing 0.1% sodium azide.

EXAMPLE 3 Elisa Procedure

[0030] Fifty microliters of affinity purified rabbit anti-rLBP antibody (2 μg/mL in PBS) were incubated overnight at 2-8° C. (or alternatively, 1 hour at 37° C.) in the wells of Immulon 2 (Dynatech Laboratories Inc., Chantilly, Va.) microtiter plates. The antibody solution was removed and 200 μL of 1% non-fat milk in PBS (blocking agent) was added to all wells. After blocking the plates for 1 hour at room temperature, the wells were washed 3 times with 300 μL of wash buffer (PBS/0.05% Tween-20).

[0031] Standards, samples and controls were diluted in triplicate with PBS containing 1% bovine serum albumin, 0.05% Tween 20 (PBS-BSA/Tween) and 10 units/mL of sodium heparin (Sigma Chemical Co., St. Louis, Mo.) in separate 96-well plates. rLBP or rLBP₂₅ standard solutions were prepared as serial two-fold dilutions from 100 to 0.012 ng/mL. Each replicate and dilution of the standards, samples and controls (50 μL) was transferred to the blocked microtiter plates and incubated for 1 hour at 37° C. After the primary incubation, the wells were washed 3 times with wash buffer. Biotin-labeled rabbit anti-LBP antibody was diluted 1/2000 in PBS-BSA/Tween and 50 μL was added to all wells. The plates were then incubated for 1 hour at 37° C. Subsequently, all wells were washed 3 times with wash buffer. Alkaline phosphatase-labeled streptavidin (Zymed Laboratories Inc., San Francisco. Calif.) was diluted 1/2000 in PBS-BSA/Tween and 50 μL was added to all wells. After incubation for 15 minutes at 37° C., all wells were washed 3 times with wash buffer and 3 times with deionized water and the chromogenic substrate p-nitrophenylphosphate (1 mg/mL in 10% diethanolamine buffer) was added in a volume of 50 μL to all wells. Color development was allowed to proceed for 1 hour at room temperature, after which 50 μL of 1 N NaOH was added to stop the reaction. The absorbance at 405 nm was determined for all wells using a Vmax Plate Reader (Molecular Devices Corp., Menlo Park, Calif.).

[0032] The mean absorbance at 405 nm (A₄₀₅) for all samples and standards (in triplicate) were corrected for background by subtracting the mean A₄₀₅ of wells receiving only sample dilution buffer (no LBP) in the primary incubation step. A standard curve was then plotted as A₄₀₅ versus ng/mL of rLBP or rLBP₂₅. The linear range was selected, a linear regression analysis was performed and concentrations were determined for samples and controls by interpolation from the standard curve.

EXAMPLE 4 Comparative Immunoreactivity of rLBP, rLBP₂₅, rBPI AND rBPI₂₃

[0033] In this example, the immunoreactivity of rLBP, rLBP₂₅, rBPI and rBPI₂₃ were compared in the BPI sandwich ELISA to determine possible immunologic cross-reactivity. Despite considerable sequence homology between LBP and BPI (see, e.g., Schumann et al., Science, 249:1429 (1990), the results illustrated in FIG. 1 show that, on a mass basis, rBPI₂₃ produced a signal which was approximately 3 orders of magnitude lower than that of rLBP₂₅ and rLBP, while rBPI produced a signal that was approximately 5 orders of magnitude lower than that of rLBP and rLBP₂₅. For example, a concentration of 100,000 ng/mL (100 μg/mL) of rBPI or 400 ng/mL rBPI₂₃ generated a signal which was equal to that produced by 0.8 ng/mL of rLBP or 0.4 ng/mL of rLBP₂₅. These results demonstrate minimal cross-reactivity of the antibody with BPI and confirm the specificity of the assay for LBP.

EXAMPLE 5 Measurement of rLBP Spiked into Pooled Human Plasma

[0034] In this example, the recovery of rLBP in human blood fluids was evaluated by examining pooled human plasma spiked with different concentrations of rLBP and then frozen and thawed prior to measurement in the sandwich ELISA. Recovery of spiked LBP was defined as the amount of LBP measured in spiked human plasma samples minus the concentration in the unspiked control, divided by the actual amount spiked in the sample. The fraction recovered was multiplied by 100 and the results were expressed as a percentage of the input concentration. Recovery of different concentrations of rLBP spiked into pooled human plasma samples averaged 68% and ranged from 59% at 42 μg/mL to 78% at 168 μg/mL. Table I summarizes the recovery data for each LBP spiked plasma sample. TABLE I Recovery of rLBP Spiked into Pooled Citrated Human Plasma Amount Spiked Amount Measured Amount Recovered Percent (μg/mL) (μg/mL) (μg/mL) Recovery 0 2.47 — — 10.5 9.85 7.38 70% 21 16.1 13.63 65% 42 27.3 24.83 59% 84 60.8 58.33 69% 168 133 130.53 78% Mean Recovery 68%

EXAMPLE 6 Comparison of Plasma and Serum LBP Levels

[0035] According to this example concentrations of LBP in the serum and plasma of healthy subjects were assayed and compared utilizing the sandwich ELISA assay according to Example 3. Plasma concentrations of LBP were found to be essentially the same as serum concentrations for LBP when the plasma volume was corrected for dilution (dividing by a factor of 0.85) resulting from the addition of anticoagulant. Plasma concentrations in normal human subjects were found to be 3.1 μg/mL (S.D. 0.9 μg/mL) or 3.7 μg/mL (S.D. 1.1 μl/mL) corrected, compared with 3.7 μg/mL (S.D. 0.9 μg/mL) for serum.

EXAMPLE 7 Clinical Correlations of Endogenous LBP Immunoreactivity in Human Plasma

[0036] In this example endogenous LBP immunoreactivity was measured in human plasma or serum samples collected from a variety of subjects suffering from gram-negative sepsis and a variety of other clinical conditions. Specifically, plasma samples of healthy individuals (59 subjects), and individuals diagnosed with gram-negative sepsis (390 subjects) were assayed for LBP levels. Serum samples of individuals with acute lymphoblastic leukemia (ALL) (6 subjects); acute graft versus host disease (aGvHD) (8 subjects); chronic lymphocytic leukemia (CLL) (9 subjects); cutaneous T-cell lymphoma (CTCL) (12 subjects); type 1 diabetes (13 subjects); aplastic anemia (AA) (16 subjects); Crohn's Disease (8 subjects); psoriasis (13 subjects); rheumatoid arthritis (RA) (86 subjects); scleroderrna (4 subjects), and systemic lupus erythematosus (SLE) (10 subjects) were assayed for LBP levels. The results are shown in FIG. 2.

[0037] In another experiment, LBP immunoreactivity was also measured in plasma samples from healthy non-pregnant women (18 subjects) and in plasma samples from age-matched pregnant women in the third trimester of gestation with no evidence of active infection (18 subjects). The mean result for the healthy non-pregnant women was 3.8 μg/mL (ranging from 1.7 to 7.7 μg/mL), which was comparable to that of the healthy individuals assayed earlier, and the mean result for the pregnant women was 10.5 μg/mL (ranging from 4.6 to 22.7 μg/mL).

[0038] In a further experiment, levels of LBP as well as C-reactive protein (an acute phase protein) were measured in plasma samples from patients diagnosed with AIDS, with no concomitant infection. The mean LBP value was 5.33±2.31 μg/mL (ranging from 2.1 to 10.3 μg/mL) and the mean CRP level was 5.34 ±6.99 μg/mL (ranging from 0.25 to 18.3 μg/mL).

[0039] While LBP levels among subjects diagnosed as suffering from gram-negative sepsis were elevated it was found that LBP levels were not substantially elevated over normal in subjects with acute lymphoblastic leukemia, acute graft versus host disease. chronic lymplhocytic leukemia, cutaneous T-cell lymphoma, type 1 diabetes, aplastic anemia. Crohn's Disease, psoriasis, rheumatoid arthritis, scleroderma, systemic lupus erythematosus (SLE), pregnancy and AIDS. Accordingly, the LBP assay of the invention is valuable for distinguishing conditions associated with endotoxin from other acute phase conditions or non-acute phase conditions not associated with endotoxin.

EXAMPLE 8 The Effect of LPS Administration on Endogenous LBP Levels in Healthy Subjects

[0040] In this example, the effect of LPS administration on endogenous LBP immunoreactivity in healthy human subjects was determined. Specifically, healthy subjects were monitored utilizing the LBP sandwich assay for changes in LEP plasma levels at various time points after intravenous administration of 4 ng/kg LPS (16 subjects) or in control subjects (2) not receiving LPS. The results illustrated in FIG. 3 show the change in mean plasma LBP concentration with time. For those subjects treated with LPS LBP levels began to rise about 6 hours after LPS administration. Peak LBP plasma levels were observed in most subjects between 10 to 12 hours after the LPS administration. The average increase from baseline to peak LBP level was approximately 3-fold. Over this time period the mean LBP levels in control subjects remained within normal range (approximately 5 μg/mL).

[0041] It is contemplated that additional analysis will illustrate the correlation of LBP levels in body fluids with the symptoms of exposure to endotoxin and that LBP levels will be diagnostic and prognostic of disease states resulting from exposure to endotoxin.

[0042] It is contemplated that additional analysis will illustrate the correlation of LBP levels with symptoms of bacterial infections, endotoxemia and sepsis including conditions associated with sepsis including DIC and ARDS.

EXAMPLE 9 Clinical Correlations Between Plasma LBP Levels and Survival in Suspected Gram-Negative Sepsis Patients

[0043] Correlations between plasma LBP levels and survival in suspected gram-negative sepsis patients were compared using data obtained from the septic subjects described in Example 7. In this case, a standard LBP concentration was set at 46 μg/mL and patients with suspected gram-negative sepsis were classified as having either high (>46 μg/mL) or low (<46 μg/mL) LBP plasma levels as measured in pretreatment samples. As shown in the data presented in FIG. 4, those subjects having low pretreatment plasma levels of LBP had a significantly greater survival rate (p=0.004) over a 27 day period than did those subjects having a high pretreatment plasma LBP level. These data show the utility of assaying LBP levels and comparing them to a standard LBP value for predicting the prognosis of subjects suffering from sepsis.

EXAMPLE 10 Clinical Correlations of Acute Phase Proteins in Healthy, Rheumatoid Arthritic, and Septic Patients

[0044] Plasma levels of LBP, C-reactive protein (CRP) and fibrinogen were measured in small groups of healthy, rheumatoid arthritic and septic patients with the results shown in FIGS. 5a (LBP levels), 5 b (CRP levels) and 5 c (fibrinogen levels). The results show that relative to healthy subjects, mean fibrinogen levels were elevated approximately 2.5 fold for both rheumatoid arthritic and septic subjects. Relative to healthy subjects, mean CRP levels were found to be elevated approximately 40-fold for rheumatoid arthritic subjects and 200-fold for septic subjects. In contrast, and consistent with the results in Example 7, mean LBP levels were only slightly increased (less than 2-fold) for rheumatoid arthritis subjects while the mean LBP levels were increased by more than 6 fold for septic subjects.

[0045] Numerous modifications and variations in the practice of the invention are expected to occur to those skilled in the art upon consideration of the foregoing description of the presently preferred embodiments thereof. Consequently, the only limitations which should be placed upon the scope of the present invention are those which appear in the appended claims.

1 4 1443 base pairs nucleic acid single linear DNA CDS 1..1443 mat_peptide 76..1443 misc_feature “rLBP” 1 ATG GGG GCC TTG GCC AGA GCC CTG CCG TCC ATA CTG CTG GCA TTG CTG 48 Met Gly Ala Leu Ala Arg Ala Leu Pro Ser Ile Leu Leu Ala Leu Leu -25 -20 -15 -10 CTT ACG TCC ACC CCA GAG GCT CTG GGT GCC AAC CCC GGC TTG GTC GCC 96 Leu Thr Ser Thr Pro Glu Ala Leu Gly Ala Asn Pro Gly Leu Val Ala -5 1 5 AGG ATC ACC GAC AAG GGA CTG CAG TAT GCG GCC CAG GAG GGG CTA TTG 144 Arg Ile Thr Asp Lys Gly Leu Gln Tyr Ala Ala Gln Glu Gly Leu Leu 10 15 20 GCT CTG CAG AGT GAG CTG CTC AGG ATC ACG CTG CCT GAC TTC ACC GGG 192 Ala Leu Gln Ser Glu Leu Leu Arg Ile Thr Leu Pro Asp Phe Thr Gly 25 30 35 GAC TTG AGG ATC CCC CAC GTC GGC CGT GGG CGC TAT GAG TTC CAC AGC 240 Asp Leu Arg Ile Pro His Val Gly Arg Gly Arg Tyr Glu Phe His Ser 40 45 50 55 CTG AAC ATC CAC AGC TGT GAG CTG CTT CAC TCT GCG CTG AGG CCT GTC 288 Leu Asn Ile His Ser Cys Glu Leu Leu His Ser Ala Leu Arg Pro Val 60 65 70 CCT GGC CAG GGC CTG AGT CTC AGC ATC TCC GAC TCC TCC ATC CGG GTC 336 Pro Gly Gln Gly Leu Ser Leu Ser Ile Ser Asp Ser Ser Ile Arg Val 75 80 85 CAG GGC AGG TGG AAG GTG CGC AAG TCA TTC TTC AAA CTA CAG GGC TCC 384 Gln Gly Arg Trp Lys Val Arg Lys Ser Phe Phe Lys Leu Gln Gly Ser 90 95 100 TTT GAT GTC AGT GTC AAG GGC ATC AGC ATT TCG GTC AAC CTC CTG TTG 432 Phe Asp Val Ser Val Lys Gly Ile Ser Ile Ser Val Asn Leu Leu Leu 105 110 115 GGC AGC GAG TCC TCC GGG AGG CCC ACA GTT ACT GCC TCC AGC TGC AGC 480 Gly Ser Glu Ser Ser Gly Arg Pro Thr Val Thr Ala Ser Ser Cys Ser 120 125 130 135 AGT GAC ATC GCT GAC GTG GAG GTG GAC ATG TCG GGA GAC TTG GGG TGG 528 Ser Asp Ile Ala Asp Val Glu Val Asp Met Ser Gly Asp Leu Gly Trp 140 145 150 CTG TTG AAC CTC TTC CAC AAC CAG ATT GAG TCC AAG TTC CAG AAA GTA 576 Leu Leu Asn Leu Phe His Asn Gln Ile Glu Ser Lys Phe Gln Lys Val 155 160 165 CTG GAG AGC AGG ATT TGC GAA ATG ATC CAG AAA TCG GTG TCC TCC GAT 624 Leu Glu Ser Arg Ile Cys Glu Met Ile Gln Lys Ser Val Ser Ser Asp 170 175 180 CTA CAG CCT TAT CTC CAA ACT CTG CCA GTT ACA ACA GAG ATT GAC AGT 672 Leu Gln Pro Tyr Leu Gln Thr Leu Pro Val Thr Thr Glu Ile Asp Ser 185 190 195 TTC GCC GAC ATT GAT TAT AGC TTA GTG GAA GCC CCT CGG GCA ACA GCC 720 Phe Ala Asp Ile Asp Tyr Ser Leu Val Glu Ala Pro Arg Ala Thr Ala 200 205 210 215 CAG ATG CTG GAG GTG ATG TTT AAG GGT GAA ATC TTT CAT CGT AAC CAC 768 Gln Met Leu Glu Val Met Phe Lys Gly Glu Ile Phe His Arg Asn His 220 225 230 CGT TCT CCA GTT ACC CTC CTT GCT GCA GTC ATG AGC CTT CCT GAG GAA 816 Arg Ser Pro Val Thr Leu Leu Ala Ala Val Met Ser Leu Pro Glu Glu 235 240 245 CAC AAC AAA ATG GTC TAC TTT GCC ATC TCG GAT TAT GTC TTC AAC ACG 864 His Asn Lys Met Val Tyr Phe Ala Ile Ser Asp Tyr Val Phe Asn Thr 250 255 260 GCC AGC CTG GTT TAT CAT GAG GAA GGA TAT CTG AAC TTC TCC ATC ACA 912 Ala Ser Leu Val Tyr His Glu Glu Gly Tyr Leu Asn Phe Ser Ile Thr 265 270 275 GAT GAG ATG ATA CCG CCT GAC TCT AAT ATC CGA CTG ACC ACC AAG TCC 960 Asp Glu Met Ile Pro Pro Asp Ser Asn Ile Arg Leu Thr Thr Lys Ser 280 285 290 295 TTC CGA CCC TTC GTC CCA CGG TTA GCC AGG CTC TAC CCC AAC ATG AAC 1008 Phe Arg Pro Phe Val Pro Arg Leu Ala Arg Leu Tyr Pro Asn Met Asn 300 305 310 CTG GAA CTC CAG GGA TCA GTG CCC TCT GCT CCG CTC CTG AAC TTC AGC 1056 Leu Glu Leu Gln Gly Ser Val Pro Ser Ala Pro Leu Leu Asn Phe Ser 315 320 325 CCT GGG AAT CTG TCT GTG GAC CCC TAT ATG GAG ATA GAT GCC TTT GTG 1104 Pro Gly Asn Leu Ser Val Asp Pro Tyr Met Glu Ile Asp Ala Phe Val 330 335 340 CTC CTG CCC AGC TCC AGC AAG GAG CCT GTC TTC CGG CTC AGT GTG GCC 1152 Leu Leu Pro Ser Ser Ser Lys Glu Pro Val Phe Arg Leu Ser Val Ala 345 350 355 ACT AAT GTG TCC GCC ACC TTG ACC TTC AAT ACC AGC AAG ATC ACT GGG 1200 Thr Asn Val Ser Ala Thr Leu Thr Phe Asn Thr Ser Lys Ile Thr Gly 360 365 370 375 TTC CTG AAG CCA GGA AAG GTA AAA GTG GAA CTG AAA GAA TCC AAA GTT 1248 Phe Leu Lys Pro Gly Lys Val Lys Val Glu Leu Lys Glu Ser Lys Val 380 385 390 GGA CTA TTC AAT GCA GAG CTG TTG GAA GCG CTC CTC AAC TAT TAC ATC 1296 Gly Leu Phe Asn Ala Glu Leu Leu Glu Ala Leu Leu Asn Tyr Tyr Ile 395 400 405 CTT AAC ACC TTC TAC CCC AAG TTC AAT GAT AAG TTG GCC GAA GGC TTC 1344 Leu Asn Thr Phe Tyr Pro Lys Phe Asn Asp Lys Leu Ala Glu Gly Phe 410 415 420 CCC CTT CCT CTG CTG AAG CGT GTT CAG CTC TAC GAC CTT GGG CTG CAG 1392 Pro Leu Pro Leu Leu Lys Arg Val Gln Leu Tyr Asp Leu Gly Leu Gln 425 430 435 ATC CAT AAG GAC TTC CTG TTC TTG GGT GCC AAT GTC CAA TAC ATG AGA 1440 Ile His Lys Asp Phe Leu Phe Leu Gly Ala Asn Val Gln Tyr Met Arg 440 445 450 455 GTT 1443 Val 481 amino acids amino acid linear protein misc_feature “rLBP” 2 Met Gly Ala Leu Ala Arg Ala Leu Pro Ser Ile Leu Leu Ala Leu Leu -25 -20 -15 -10 Leu Thr Ser Thr Pro Glu Ala Leu Gly Ala Asn Pro Gly Leu Val Ala -5 1 5 Arg Ile Thr Asp Lys Gly Leu Gln Tyr Ala Ala Gln Glu Gly Leu Leu 10 15 20 Ala Leu Gln Ser Glu Leu Leu Arg Ile Thr Leu Pro Asp Phe Thr Gly 25 30 35 Asp Leu Arg Ile Pro His Val Gly Arg Gly Arg Tyr Glu Phe His Ser 40 45 50 55 Leu Asn Ile His Ser Cys Glu Leu Leu His Ser Ala Leu Arg Pro Val 60 65 70 Pro Gly Gln Gly Leu Ser Leu Ser Ile Ser Asp Ser Ser Ile Arg Val 75 80 85 Gln Gly Arg Trp Lys Val Arg Lys Ser Phe Phe Lys Leu Gln Gly Ser 90 95 100 Phe Asp Val Ser Val Lys Gly Ile Ser Ile Ser Val Asn Leu Leu Leu 105 110 115 Gly Ser Glu Ser Ser Gly Arg Pro Thr Val Thr Ala Ser Ser Cys Ser 120 125 130 135 Ser Asp Ile Ala Asp Val Glu Val Asp Met Ser Gly Asp Leu Gly Trp 140 145 150 Leu Leu Asn Leu Phe His Asn Gln Ile Glu Ser Lys Phe Gln Lys Val 155 160 165 Leu Glu Ser Arg Ile Cys Glu Met Ile Gln Lys Ser Val Ser Ser Asp 170 175 180 Leu Gln Pro Tyr Leu Gln Thr Leu Pro Val Thr Thr Glu Ile Asp Ser 185 190 195 Phe Ala Asp Ile Asp Tyr Ser Leu Val Glu Ala Pro Arg Ala Thr Ala 200 205 210 215 Gln Met Leu Glu Val Met Phe Lys Gly Glu Ile Phe His Arg Asn His 220 225 230 Arg Ser Pro Val Thr Leu Leu Ala Ala Val Met Ser Leu Pro Glu Glu 235 240 245 His Asn Lys Met Val Tyr Phe Ala Ile Ser Asp Tyr Val Phe Asn Thr 250 255 260 Ala Ser Leu Val Tyr His Glu Glu Gly Tyr Leu Asn Phe Ser Ile Thr 265 270 275 Asp Glu Met Ile Pro Pro Asp Ser Asn Ile Arg Leu Thr Thr Lys Ser 280 285 290 295 Phe Arg Pro Phe Val Pro Arg Leu Ala Arg Leu Tyr Pro Asn Met Asn 300 305 310 Leu Glu Leu Gln Gly Ser Val Pro Ser Ala Pro Leu Leu Asn Phe Ser 315 320 325 Pro Gly Asn Leu Ser Val Asp Pro Tyr Met Glu Ile Asp Ala Phe Val 330 335 340 Leu Leu Pro Ser Ser Ser Lys Glu Pro Val Phe Arg Leu Ser Val Ala 345 350 355 Thr Asn Val Ser Ala Thr Leu Thr Phe Asn Thr Ser Lys Ile Thr Gly 360 365 370 375 Phe Leu Lys Pro Gly Lys Val Lys Val Glu Leu Lys Glu Ser Lys Val 380 385 390 Gly Leu Phe Asn Ala Glu Leu Leu Glu Ala Leu Leu Asn Tyr Tyr Ile 395 400 405 Leu Asn Thr Phe Tyr Pro Lys Phe Asn Asp Lys Leu Ala Glu Gly Phe 410 415 420 Pro Leu Pro Leu Leu Lys Arg Val Gln Leu Tyr Asp Leu Gly Leu Gln 425 430 435 Ile His Lys Asp Phe Leu Phe Leu Gly Ala Asn Val Gln Tyr Met Arg 440 445 450 455 Val 591 base pairs nucleic acid single linear DNA CDS 1..591 misc_feature “rLBP25” 3 GCC AAC CCC GGC TTG GTC GCC AGG ATC ACC GAC AAG GGA CTG CAG TAT 48 Ala Asn Pro Gly Leu Val Ala Arg Ile Thr Asp Lys Gly Leu Gln Tyr 1 5 10 15 GCG GCC CAG GAG GGG CTA TTG GCT CTG CAG AGT GAG CTG CTC AGG ATC 96 Ala Ala Gln Glu Gly Leu Leu Ala Leu Gln Ser Glu Leu Leu Arg Ile 20 25 30 ACG CTG CCT GAC TTC ACC GGG GAC TTG AGG ATC CCC CAC GTC GGC CGT 144 Thr Leu Pro Asp Phe Thr Gly Asp Leu Arg Ile Pro His Val Gly Arg 35 40 45 GGG CGC TAT GAG TTC CAC AGC CTG AAC ATC CAC AGC TGT GAG CTG CTT 192 Gly Arg Tyr Glu Phe His Ser Leu Asn Ile His Ser Cys Glu Leu Leu 50 55 60 CAC TCT GCG CTG AGG CCT GTC CCT GGC CAG GGC CTG AGT CTC AGC ATC 240 His Ser Ala Leu Arg Pro Val Pro Gly Gln Gly Leu Ser Leu Ser Ile 65 70 75 80 TCC GAC TCC TCC ATC CGG GTC CAG GGC AGG TGG AAG GTG CGC AAG TCA 288 Ser Asp Ser Ser Ile Arg Val Gln Gly Arg Trp Lys Val Arg Lys Ser 85 90 95 TTC TTC AAA CTA CAG GGC TCC TTT GAT GTC AGT GTC AAG GGC ATC AGC 336 Phe Phe Lys Leu Gln Gly Ser Phe Asp Val Ser Val Lys Gly Ile Ser 100 105 110 ATT TCG GTC AAC CTC CTG TTG GGC AGC GAG TCC TCC GGG AGG CCC ACA 384 Ile Ser Val Asn Leu Leu Leu Gly Ser Glu Ser Ser Gly Arg Pro Thr 115 120 125 GTT ACT GCC TCC AGC TGC AGC AGT GAC ATC GCT GAC GTG GAG GTG GAC 432 Val Thr Ala Ser Ser Cys Ser Ser Asp Ile Ala Asp Val Glu Val Asp 130 135 140 ATG TCG GGA GAC TTG GGG TGG CTG TTG AAC CTC TTC CAC AAC CAG ATT 480 Met Ser Gly Asp Leu Gly Trp Leu Leu Asn Leu Phe His Asn Gln Ile 145 150 155 160 GAG TCC AAG TTC CAG AAA GTA CTG GAG AGC AGG ATT TGC GAA ATG ATC 528 Glu Ser Lys Phe Gln Lys Val Leu Glu Ser Arg Ile Cys Glu Met Ile 165 170 175 CAG AAA TCG GTG TCC TCC GAT CTA CAG CCT TAT CTC CAA ACT CTG CCA 576 Gln Lys Ser Val Ser Ser Asp Leu Gln Pro Tyr Leu Gln Thr Leu Pro 180 185 190 GTT ACA ACA GAG ATT 591 Val Thr Thr Glu Ile 195 197 amino acids amino acid linear protein misc_feature “rLBP25” 4 Ala Asn Pro Gly Leu Val Ala Arg Ile Thr Asp Lys Gly Leu Gln Tyr 1 5 10 15 Ala Ala Gln Glu Gly Leu Leu Ala Leu Gln Ser Glu Leu Leu Arg Ile 20 25 30 Thr Leu Pro Asp Phe Thr Gly Asp Leu Arg Ile Pro His Val Gly Arg 35 40 45 Gly Arg Tyr Glu Phe His Ser Leu Asn Ile His Ser Cys Glu Leu Leu 50 55 60 His Ser Ala Leu Arg Pro Val Pro Gly Gln Gly Leu Ser Leu Ser Ile 65 70 75 80 Ser Asp Ser Ser Ile Arg Val Gln Gly Arg Trp Lys Val Arg Lys Ser 85 90 95 Phe Phe Lys Leu Gln Gly Ser Phe Asp Val Ser Val Lys Gly Ile Ser 100 105 110 Ile Ser Val Asn Leu Leu Leu Gly Ser Glu Ser Ser Gly Arg Pro Thr 115 120 125 Val Thr Ala Ser Ser Cys Ser Ser Asp Ile Ala Asp Val Glu Val Asp 130 135 140 Met Ser Gly Asp Leu Gly Trp Leu Leu Asn Leu Phe His Asn Gln Ile 145 150 155 160 Glu Ser Lys Phe Gln Lys Val Leu Glu Ser Arg Ile Cys Glu Met Ile 165 170 175 Gln Lys Ser Val Ser Ser Asp Leu Gln Pro Tyr Leu Gln Thr Leu Pro 180 185 190 Val Thr Thr Glu Ile 195 

What is claimed is:
 1. A method for specifically determining exposure of a subject to endotoxin comprising the steps of determining the concentration of lipopolysaccharide binding protein in a sample of body fluid from the subject and correlating the concentration of lipopolysaccharide binding protein with a standard indicative of the exposure to endotoxin.
 2. The method of claim 1 wherein said sample is a blood sample.
 3. The method of claim 1 wherein said sample is a plasma or serum sample.
 4. The method of claim 1 wherein the concentration of lipopolysaccharide binding protein is determined by means of an immunoassay.
 5. The method of claim 1 wherein the subject is pregnant.
 6. The method of claim 1 wherein the subject has acute lymphoblastic leukemia.
 7. The method of claim 1 wherein the subject has acute graft versus host disease.
 8. The method of claim 1 wherein the subject has chronic lymphocytic leukemia.
 9. The method of claim 1 wherein the subject has cutaneous T-cell lymphoma.
 10. The method of claim 1 wherein the subject has type 1 diabetes.
 11. The method of claim 1 wherein the subject has aplastic anemia.
 12. The method of claim 1 wherein the subject has Crohn's Disease.
 13. The method of claim 1 wherein the subject has psoriasis.
 14. The method of claim 1 wherein the subject has rheumatoid arthritis.
 15. The method of claim 1 wherein the subject has scleroderma.
 16. The method of claim 1 wherein the subject has systemic lupus erythematosus.
 17. The method of claim 1 wherein the subject has acquired immune deficiency syndrome (AIDS). 